1. Field of the Invention
The present invention generally relates to a method and apparatus for making ophthalmic lenses, and more particularly, to a method and apparatus for making opthalmic lenses, particularly contact lenses, using a vacuum injection process.
2. Description of the Related Art
Conventionally, a contact lens is molded using a two-sided mold in which one side of the mold includes a convex surface and the other side of the mold includes an opposing concave surface, and in which a cavity for forming the lens is defined by the opposing convex and concave surfaces. A lens is formed by placing a lens material on one of the convex and concave surfaces, bringing the two sides of the mold together to form the lens cavity and separating the two sides of the mold to expose the molded lens after polymerization of the lens material.
This conventional technique, however, suffers various drawbacks.
For example, in manufacturing the contact lens, lens material of a sufficient quantity to exceed the volume of the lens cavity is placed on one of the mold surfaces, and then the two sides of the mold are brought together to form the lens cavity. The quantity of excess lens material is collected along the outer periphery of the mold external the lens cavity to form a ring of excess polymerized lens material. This excess lens material is then uneconomically discarded as waste.
Further, since the excess lens material is forced from the lens cavity as the two sides of the mold are brought together, and since as a result the annular rims of the two sides of the mold are brought together with lens material interposed therebetween, occasionally lens material will be trapped between the annular rims of the two sides of the mold to disadvantageously cause flash along the outer edge of the molded lens.
Also, when the lens material is placed on one of the convex and concave surfaces, on occasion an air bubble will form between the lens material and the convex or concave surface. Such an air bubble can remain trapped in the mold cavity as the two sides of the mold are brought together, thus causing a defect in the molded lens after polymerization.